1. Field of the Invention
The present invention relates to an image producing apparatus and an image producing method for producing an image by forming dots in a plurality of colors on a recording medium.
2. Description of the Related Art
With significant advances in inkjet technology in recent years, it is becoming possible for inkjet image producing apparatus to produce large color prints of high quality at high speeds. Inkjet image producing apparatus are widely used particularly in sign and display applications, and are applicable to, for example, prints on POP (Point Of Purchase) posters, wall posters, outdoor advertisements, billboards, etc. Such inkjet image producing apparatus are capable of producing prints by forming a number of ink dots on a recording medium, by applying droplets made up from a plurality of inks to the recording medium.
If an inkjet image producing apparatus is designed to produce images at higher speeds and to achieve a higher density of dots, then the inkjet image producing apparatus tends to suffer from problems due to interference between ink droplets that are deposited on the recording medium. Interference between deposited ink droplets refers to a phenomenon in which, before an ink droplet that has been deposited on the image producing surface of a recording medium becomes fully fixed to the image producing surface, a subsequent ink droplet is deposited on the image producing surface in the vicinity of the prior ink droplet, whereby the prior and subsequent ink droplets combine with one another. If the ink droplets are combined with each other in this manner, the ink droplets become shifted and united together under surface tension. Since at this time the center of gravity of the dot formed by the subsequent ink droplet is displaced, the resultant image is likely to suffer from low granularity and gloss irregularities, resulting in poor image quality and appearance.
Various inkjet technologies have been proposed for appropriately controlling recording heads for expelling ink droplets to produce high-quality images in view of the adverse effects caused by interference between deposited ink droplets on the images.
According to Japanese Laid-Open Patent Publication No. 2005-313635, there has been proposed a method of and an apparatus for controlling ejection of ink droplets, so as to deliver the in droplets in successively greater amounts of ink upon successive discharge of the ink droplets from a recording head. The ink droplets, which are expelled in successively greater amounts of ink, are able to produce a line image having a uniform width on a recording medium, even if the ink droplets interfere with each other in a case where the ink droplets are deposited on the recording medium.